John McCain, the senior senator from Arizona and former Republican presidential candidate, has added his voice to the growing chorus of lawmakers seeking to block the Pentagon’s plans to retire the A-10 attack plane.

The Air Force in its budget request for fiscal 2015, which begins Oct. 1, has recommended retiring its fleet of the Cold War-era aircraft, known officially as the Thunderbolt II and unofficially as the Warthog. Its snub-nose packs a 30mm cannon designed to destroy tanks and other ground targets.

The service estimates it will save $3.7 billion over five years by retiring the almost 300 A-10s that remain in the inventory. An increasingly vocal group of lawmakers, which now includes McCain, has opposed the move on grounds that the aircraft is critical to protecting ground troops. The plane is credited with saving the lives of numerous service members, most recently in Iraq and Afghanistan.

“We are going to do away with the finest close-air-support weapon in history?” McCain said at a news conference Thursday on Capitol Hill, where he was joined by other lawmakers and even former Warthog pilots and joint terminal air attack controllers who favor keeping the plane.

The senator, a longtime critic of the F-35 fighter jet – the Pentagon’s most expensive weapons acquisition program designed to replace the A-10 and other aircraft – questioned why the Air Force would begin to get rid of the Warthog before it has started operational flights of the stealthy, radar-evading jet. The F-35A is scheduled to reach initial operating capability, or IOC, in 2016 but only by employing a less lethal version of software.

“And we are then going to have some kind of nebulous idea of a replacement with an airplane that costs at least 10 times as much — and the cost is still growing — with the F-35?” McCain said at the news conference. “That’s ridiculous.”

The Pentagon plans to spend almost $400 billion buying 2,457 F-35 Lightning IIs made by Lockheed Martin Corp. to replace such aircraft as the F-16, A-10, F/A-18 and AV-8B. The Joint Strike Fighter program has had repeated cost overruns and schedule delays due to hardware and software problems.

Still, the fifth-generation fighter jet is designed in part to operate in areas with sophisticated enemy air defenses, known in military parlance as anti-access, area-denial, or A2-AD, environments. Countries with such technology include China, North Korea and Iran.

The Warthog, meanwhile, is a slow-flying gunship designed during the Vietnam War. The A-10 entered military service in the late 1970s, though flew more recently in Iraq, Afghanistan and Libya. While it has a reputation for being tough and able to withstand damage from flak, the plane is vulnerable to shoulder-fired surface-to-air missiles, or SAMs, and other air defenses.

The Air Force maintains Warthog squadrons in several states in the U.S., and at bases in Germany and South Korea. The service has about 283 of the aircraft across the active, National Guard and Reserve components.

The Air Force in recent years spent more than $1 billion upgrading the A-10 fleet. Boeing Co. received contracts worth hundreds of millions of dollars to replace the aircraft’s wings. Northrop Grumman Corp. last fall received an order to modernize the weapons system to keep it viable through 2028.

To find long-term budget savings, however, service leaders such as Air Force Chief of Staff Gen. Mark Welsh – a former A-10 pilot himself – have weighed shedding the fleets of “single-mission” aircraft – not only the A-10, but also KC-10 refueling tankers and F-15C fighter jets.

“Even if an additional $4 billion became available, I believe the combatant commanders would all tell you that they’d rather have us fund more ISR and airborne command and control capability than retain the A-10 fleet,” Welsh said on Thursday during a hearing of the Senate Armed Services Committee, referring to the acronym for intelligence, surveillance and reconnaissance.

Winslow Wheeler, a longtime defense analyst who’s now a staff member at the Project On Government Oversight, a watchdog group in Washington, D.C., said the debate over the A-10 has become one of the top issues in this year’s congressional defense legislation. He supports keeping the aircraft.

“Gen. Welsh has kicked over a bee’s nest,” he said in a telephone interview. “He surely thought that there would be some controversy to dumping the A-10 fleet, but not what he has found he has gotten himself into.”

McCain this week joined fellow Republican Sens. Saxby Chambliss of Georgia and Kelly Ayotte of New Hampshire in writing an op-ed, “Retiring the A-10 Early Puts Troops’ Lives at Risk.”

Ayotte, whose husband was a Warthog pilot, has led the congressional fight to keep the aircraft over the past several months, with a letter-writing campaign and legislative amendment to temporarily block the Air Force from doing so. Her ability to enlist McCain into the battle is significant, Wheeler said.

“McCain is a big fish and he was sitting on the sidelines until very recently,” he said. “He brings a lot of his stature to the issue.”